Banging in the airing cupboard

[corse]

Newbie here and apologies if I'm a little vague but I am away from home at present so can only go on what my wife says!!!

She says that there was a banging noise coming from the airing cupboard and that the central heating pump was red hot.
I told her to turn it all off and stick the immersion heater on for the hot water.

Now the system had started to play up recently (possibly connected?) for when I turned the heating off at the timer around the end of April, I noticed that one of the top radiators (we live in a split level house over 4 floors!) was warm even though the CH was off?

The pump is a Grundfos one I definitely know but no idea of its age as the system is what we inherited when we moved in a couple of years ago.
The boiler is fairly old too - maybe original?? (house was built in 1996) but is serviced once a year. I can give you more info when I get back tomorrow if needed but in the meantime, I was wondering what the problem could be??
I would assume the banging could be air??

Cheers

 

[CombustionGuy]

Or the system is boiling.( pump stuck or not working)

Or the zone valve isn't shutting fully and jumping and making a noice

 

[corse]

Thanks for the reply,
I have long suspected the zone / 3 way valve due to one of the radiators coming on whilst only having the hot water on.
I did not hear the banging noise but my wife says it was like the pipes in the airing cupboard were 'jumping'?
If I get the valve replaced, would there be any damage to the pump as that was 'apparently' red hot?? and get that replaced at the same time??

Thanks for your help/advice.

 

[longdogs]

Was it a neighbour?